Learning how to close and winterize an above ground pool the right way can save you hundreds of dollars in freeze damage and hours of frustration when spring rolls around. I have helped neighbors and friends winterize their pools for over a decade, and the process comes down to timing, proper chemical balance, and protecting your equipment from ice expansion. Skip a step, and you could be looking at a cracked skimmer, a torn liner, or a burnt-out pump motor by the time the thaw hits.
The right time to close your pool is when the water temperature consistently stays at or below 65 degrees Fahrenheit. Some pool owners in northern climates target 60 degrees as their cutoff point. Closing too early traps warm water under the cover, which encourages algae growth all winter long. Closing too late risks freeze damage during an unexpected cold snap.
Every above ground pool in a region where temperatures drop below freezing needs annual winterization. This includes pools with metal frames, resin frames, inflatable ring pools, and saltwater systems. The process typically takes one full afternoon if you have all your supplies ready ahead of time and have a helper for the cover installation step.
In this guide, I will walk you through every step of above ground pool winterization, from building your supplies checklist to installing the winter cover and air pillow. You will learn the exact chemical levels to target, how low to drop the water, and the common mistakes that ruin pools every winter.
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Before you start the winterization process, gather every supply on this checklist. Running to the pool store mid-process means your chemicals will not have time to circulate properly, and you risk losing daylight if you are closing in late fall.
You will need pool shock (chlorine or non-chlorine), winter algaecide, a sequestering agent or stain and scale remover, and a winterizing chemical kit sized for your pool volume. Most kits cover pools between 7,500 and 35,000 gallons, so check the label before buying. pH increaser (soda ash) and pH decreaser (muriatic acid or sodium bisulfate) are needed for balancing water chemistry before you add the winter chemicals.
Get a winter cover sized specifically for your pool dimensions with enough overlap to account for the air pillow. You will also need cover cables, a winch or tensioner, winter cover seal, and a cover pump for removing rainwater and snowmelt during the off-season. For plumbing protection, pick up a skimmer winterizing plate, threaded winterizing plugs for your return jets, and Teflon tape for sealing threaded connections.
A pool brush, leaf skimmer net, and vacuum head with telescoping pole are essential for the cleaning phase. You will also need an air pillow (also called an ice compensator), a submersible pump or drain pump for lowering the water level, and absorbent socks or aqua blocks for extra cover weight if you live in a windy area. If you use a pool cleaner for maintenance during the season, remove it and store it separately.
Follow these nine steps in order. Each step builds on the previous one, and skipping or reordering them can lead to poor results or equipment damage.
Start by skimming all leaves, bugs, and surface debris from the water with your leaf net. Leaves left in the pool over winter will sink, decompose, and stain your liner. Brush the walls and floor to break up any algae or biofilm that has started forming, then vacuum the entire pool to remove settled debris.
Pay extra attention to the corners and around the skimmer opening where debris collects. A clean pool means your winterizing chemicals will work at full strength instead of being consumed by organic matter. This step alone makes a huge difference in how clean your pool looks when you open it next spring.
Test your water using a reliable test kit or test strips. You need to hit these target ranges before adding any winterizing chemicals:
pH: 7.2 to 7.8 (ideal is 7.4 to 7.6)
Total alkalinity: 80 to 120 ppm
Calcium hardness: 180 to 220 ppm
Chlorine: 1.0 to 3.0 ppm
Adjust pH first, then alkalinity, then calcium hardness. If your alkalinity is too low, add baking soda (sodium bicarbonate) at 1.5 pounds per 10,000 gallons to raise it approximately 10 ppm. If pH is too high, add pH decreaser gradually and retest after each addition. Run the pump for at least one hour between adjustments so the chemicals circulate fully before you retest.
Once your water is balanced, add your winterizing chemicals in this specific order to avoid reactions between incompatible products:
Shock the pool with chlorine shock or non-chlorine shock. Use one pound of shock per 10,000 gallons of water. Pour it slowly around the perimeter of the pool while the pump is running.
Wait at least 1 hour for the shock to circulate before adding the next chemical. This prevents the chlorine from neutralizing your algaecide.
Add a sequestering agent or stain and scale remover to prevent metals and minerals from settling and staining the liner during winter. Follow the dosage instructions on the bottle.
Add winter algaecide as the final chemical. Use a concentrated algaecide rated for winter use, typically poured around the pool edges. Run the pump for another 30 minutes to distribute it evenly.
Do not mix chemicals directly in one spot. Add them one at a time, walking around the pool perimeter to ensure even distribution. Overdosing any single chemical can damage your liner or cause staining that will not come off in spring.
Lower the water level to approximately 4 to 6 inches below the lowest return jet or skimmer opening. For most above ground pools, this means dropping the water 4 to 6 inches below the through-wall skimmer. Use a submersible pump or your filter system's waste setting to drain the excess water.
WARNING: Never drain your above ground pool completely. Draining the pool removes the structural support that water provides to the pool walls. An empty above ground pool can collapse under wind load or shift on its base, especially in areas with freeze-thaw cycles. The water also insulates the liner from extreme cold and prevents the vinyl from becoming brittle and cracking.
This is one of the biggest sources of confusion for first-time pool owners. The pool pump and filter should be drained separately from the pool itself. You are protecting the equipment from freeze damage while leaving enough water in the pool to maintain wall structure and liner integrity.
Take out all removable accessories including ladders, steps, thermometers, pool cleaners, skimmer baskets, and any toys or floats. Clean each item with fresh water and mild soap before storing. Pool ladders and steps should be stored indoors or in a dry shed to prevent rust and UV damage.
If you are looking at replacement pool ladder options for next season, inspect your current ladder for rust and stress cracks during removal. Stainless steel hardware should be dried thoroughly and lightly coated with silicone lubricant to prevent corrosion during storage.
This is the most critical step for preventing freeze damage. Turn off the power to your pump and filter system at the breaker before starting. Drain the pump by removing the drain plugs at the bottom of the pump housing. Remove the pump basket and store it indoors.
Drain your filter tank completely. For sand filters, remove the drain cap and let the water flow out, then set the multiport valve to the closed position. For cartridge filters, remove the cartridge, clean it thoroughly, and store it indoors where it will not freeze. If you need to replace your filter, check our guide on the best pool sand filters for maintenance to find one that suits your pool size.
Disconnect all hoses between the skimmer, pump, filter, and return jets. Blow out each hose with a shop vacuum or air compressor to remove all residual water. Water left inside hoses will freeze, expand, and split the hose walls. Store all hoses and fittings indoors in a dry location.
If your pool has a heater, drain it completely and blow out the heat exchanger. Check out our pool heat pump maintenance guide for detailed instructions on protecting heating equipment during winter.
With the water lowered and equipment disconnected, seal all plumbing openings to prevent water from entering the lines. Install a skimmer winterizing plate over the skimmer face using the existing screws. This plate creates a watertight seal that prevents rain and snowmelt from entering the skimmer housing and freezing.
Threaded winterizing plugs go into the return jet fittings inside the pool. Wrap the threads with Teflon tape for a tighter seal. Push the plug in firmly and hand-tighten. Do not over-tighten, as you can crack the fitting on resin pools. An alternative to plugs is a return jet winterizing plate, which screws over the return fitting from inside the pool.
If your pool uses a through-wall skimmer instead of a hang-on skimmer, the winterizing plate replaces the skimmer basket and faceplate. Some pool owners use a skimmer guard or Gizzmo, which is a hollow tube that screws into the skimmer and absorbs ice expansion pressure inside the skimmer housing.
An air pillow, also called an ice compensator, sits in the center of your pool under the winter cover. It serves two purposes: it absorbs the expansion of ice as water freezes, and it creates a slope on the winter cover so rainwater and debris slide off toward the edges instead of pooling in the center.
Inflate the air pillow to about 60 percent capacity. Do not fully inflate it, because cold temperatures will cause the air inside to contract and a fully inflated pillow could pop. Position the pillow in the center of the pool and secure it with string or rope tied to the pool uprights. Use at least two anchor points to keep it centered.
The general rule is to use one air pillow for round pools up to 24 feet and two pillows for larger or oval pools. Some pool owners skip the air pillow, but I strongly recommend using one. The cost of a pillow is minimal compared to the risk of ice damage to your pool walls or liner.
Drape the winter cover over the pool with the air pillow centered underneath. The cover should have at least 12 inches of overlap beyond the pool wall on all sides. Secure the cover with a cable threaded through the grommets and tightened with a winch or ratcheting tensioner.
For extra security against wind, apply winter cover seal tape around the top rail of the pool where the cover meets the wall. Some pool owners also use cover clips or wall bags filled with water positioned around the perimeter. In windy areas, cover clips every 8 to 12 inches prevent the cover from billowing and tearing.
Position a cover pump on top of the cover to automatically remove rainwater and snowmelt as it accumulates. Excess water weight on the cover is the number one cause of winter cover failure. Check the cover pump every few weeks during winter to make sure it is functioning properly.
Even experienced pool owners make errors during winterization. Here are the most costly mistakes and how to avoid them.
This cannot be stressed enough. Never drain your above ground pool below the recommended level. The water pressure against the walls is what keeps an above ground pool structurally stable. Without water, the walls can buckle under wind load, the base can shift, and the liner can shrink and pull away from the walls. Repairs from a wall collapse often cost more than replacing the entire pool.
Closing your pool while water temperatures are still above 65 degrees Fahrenheit invites algae problems. The warm water under the cover becomes a breeding ground for algae even with winterizing chemicals. You will open to a green pool in spring. Wait until the water temperature is consistently in the low 60s before closing.
On the flip side, waiting too long risks freeze damage. If an unexpected hard freeze hits before you have drained your equipment and disconnected hoses, you could crack your pump housing, split a filter tank, or burst a plumbing line. Watch the weather forecast closely as fall progresses.
Some pool owners assume that a covered pool does not need chemicals. This is wrong. Without winterizing chemicals, algae and bacteria will grow slowly all winter. By spring, the water will be green, the liner will be stained, and you will spend significantly more on chemicals to recover than you would have spent on winterizing chemicals.
Water left inside the pump, filter, or hoses will freeze and expand. This expansion creates cracks that may not be visible until you start the system in spring. By then, the damage is done and the equipment needs replacement. Take the time to blow out every line and drain every component thoroughly.
A winter cover is not a set-it-and-forget-it item. Check it every few weeks for water accumulation, tears, and security. Use a cover pump to remove standing water. Clear off heavy snow loads before they stress the cover material. A neglected cover can tear, sink into the pool, and allow debris to contaminate your water all winter.
Once your pool is closed, a small amount of ongoing maintenance will protect your investment through the coldest months.
Check the cover weekly during fall when leaves are dropping. Remove debris with a soft broom or leaf blower. Do not let leaves sit on the cover all winter, because they decompose and create a messy sludge that stains the cover material.
Monitor the cover pump throughout winter. Ice can form around the pump intake and block it. After heavy rain or snowmelt, verify that the pump is removing water from the cover surface. If you live in a region with heavy snowfall, periodically clear excess snow from the cover to prevent excess weight from pulling the cover into the pool.
Inspect the cover cable tension once a month. Temperature changes cause the cable to expand and contract, which can loosen the cover. Re-tighten with your winch as needed to keep the cover secure against the pool walls.
Above ground pools are generally easier to winterize than inground pools. Above ground pools do not require blowing out underground plumbing lines, and the equipment is typically above the water level, making drainage simpler. However, above ground pools are more vulnerable to wall collapse if drained improperly.
Inground pools require professional-grade air compressors to blow out underground plumbing, and the antifreeze used in inground lines is not typically needed for above ground setups. Above ground pool owners can generally complete the entire winterization process themselves without specialized equipment beyond a shop vacuum.
Saltwater pools require one additional step. The salt cell generator should be removed, cleaned with a mild acid solution, and stored indoors. Saltwater does not freeze at the same temperature as fresh water, but the generator cell will be damaged if left outside during freezing weather.
Yes, you should always add winterizing chemicals before closing your pool. Winter shock kills bacteria and contaminants, algaecide prevents algae growth during dormancy, and a sequestering agent prevents metal staining on the liner. Skipping chemicals almost always results in a green, stained pool come spring.
If you do not winterize your pool, freezing temperatures will expand water inside the pump, filter, and plumbing lines, cracking the equipment housings and splitting hoses. The pool walls can sustain ice damage, and the liner may become brittle and tear. You will also face severe algae growth and debris accumulation, making spring opening extremely difficult and expensive.
Add chlorine or non-chlorine shock (1 lb per 10,000 gallons), a sequestering agent or stain and scale remover, and concentrated winter algaecide. Add them in that order with at least one hour of pump circulation between the shock and algaecide. A complete winterizing kit has all the chemicals you need in pre-measured doses.
No, you should never close an above ground pool without a proper winter cover. Without a cover, leaves, debris, and animals will contaminate the water all winter. UV exposure will degrade the liner, and the pool will be unsafe. A winter cover is essential for protecting both the water quality and the pool structure.
Lower the water level to 4 to 6 inches below the lowest return jet or skimmer opening. Never drain the pool completely, as the water provides structural support to the walls. Partially draining prevents water from entering the plumbing lines while keeping enough water in the pool to maintain wall and liner integrity.
Add chemicals in this order: first balance pH and alkalinity, then add shock treatment, wait at least one hour for circulation, then add a sequestering agent, and finally add winter algaecide. Run the pump between each addition to ensure proper distribution before adding the next chemical.
Knowing how to close and winterize an above ground pool properly is the difference between a smooth spring opening and a costly repair job. The process comes down to five core actions: clean the pool, balance the water, add winterizing chemicals, protect the equipment from freezing, and install a secure cover with an air pillow.
Remember the critical rules: never drain the pool completely, wait until water temperatures are consistently below 65 degrees Fahrenheit, and always remove every drop of water from your pump, filter, and hoses. Check your cover periodically throughout winter for water accumulation and debris load.
When spring arrives and it is time to open, you will thank yourself for doing the job right. A properly winterized pool typically needs only a basic shock treatment and debris removal to be swim-ready, while a poorly closed pool can take weeks of chemical treatments and cleaning to recover. Take one afternoon this fall to do it right, and enjoy a hassle-free opening next season.